arXiv subjects

T. Weier

Publications and source records attributed to T. Weier.

13 recordsLinked to original sources

arXiv2026

An optimized tidal-trigger model of the QBO, and some implications for the Carrington event

Magneto-Rossby waves in the solar tachocline are currently being discussed as a potential cause of the quasi-biennial oscillation (QBO). By analyzing sequences of ground-level enhancement (GLE) events and S-flares, the dominant period of the QBO was recently shown to be close to 1.723 years, which is the dominant beat between the periods of the two-planet spring tides of Venus, Earth and Jupiter. We improve upon this model by taking into account the dependence of the three tidally-triggered magneto-Rossby waves on the actual strength of the toroidal field at the tachocline, which we infer from the averaged monthly sunspot number. When optimizing the parameters of this magnetic-field dependence, the correlation of the tidal-forcing function with the 109 extreme solar events reaches values of up to 0.8. This is much higher than the corresponding value for the field-independent tidal forcing function (appr. 0.4), and also higher than the correlation with the sunspot number (appr. 0.56). Based on this improved model, we discuss some interesting parallels between the Carrington event of 1859 and the clustering of strong solar events in summer and autumn 1989. We also make some cautious forecasts for the remainder of cycle 25.

astro-ph.SR↗

arXiv2026

Tidal triggers and the predictability of solar activity

Magneto-Rossby waves in the solar tachocline are currently considered to be one of the main determinants of solar activity. In particular, they can give rise to the quasi-biennial oscillation (QBO). The latter was recently shown to be dominated by a phase-stable period of around 1.7 years. By analyzing 72 ground-level enhancement (GLE) events and 37 S-flares, we determine that this period is close to 1.723 years. This, in turn, is the dominant beat between the periods of the spring tides of the tidally dominant planets Venus, Earth, and Jupiter, which are suspected to synchronize not only the QBO, but also the 11.07-year Schwabe cycle. We demonstrate that recent events, such as the solar storm of 2024 May 10 and the strong X-flare of 2026 February 1, align well with maxima of the combined tidal forcing.

astro-ph.SR↗

arXiv2025

Reappraising the Elatina series: What if the Solar Interpretation Were Correct?

We revisit the sedimentary laminae from the Neoproterozoic Elatina Formation of South Australia. These were first interpreted as varves driven by solar activity and later as tidalites formed by tidal processes, although the debate has remained open. This series exhibits remarkably consistent periodicities, including a primary and a secondary period of approximately 12 and 314 laminae, respectively. Our present analysis reveals a statistically significant negative correlation between the length of a cycle and the amplitude of the subsequent cycle. By analyzing the residuals of the series' minima with respect to a linear trend and calculating Dicke's ratio, we show that this series exhibits a high degree of phase stability, except for a single break-point which possibly indicates a 90{\deg} phase shift. As these findings are difficult to reconcile with the tidal model, we reconsider the original interpretation as solar-driven sedimentation and tentatively discuss it in terms of a recently developed synchronization model of the solar dynamo. This model is used to calculate the orbital periods of Venus, Earth, Jupiter and Saturn that would be required to explain the 12-year cycle, when interpreted as a modified solar Schwabe cycle, and the 314-year cycle, when interpreted as a prolonged Suess-de Vries cycle. Assuming that the sums of the angular momenta of Jupiter and Saturn and Venus and Earth are pairwise conserved, we find that the planetary orbits change surprisingly little. The plausibility of such changes over a period of seven hundred million years is discussed in light of solar system dynamics.

astro-ph.SR↗

arXiv2025

Adding further pieces to the synchronization puzzle: QBO, bimodality, and phase jumps

This work builds on a recently developed self-consistent synchronization model of the solar dynamo which attempts to explain Rieger-type periods, the Schwabe/Hale cycle and the Suess-de Vries and Gleissberg cycles in terms of resonances of various wave phenomena with gravitational forces exerted by the orbiting planets. We start again from the basic concept that the spring tides of the three pairs of the tidally dominant planets Venus, Earth and Jupiter excite magneto-Rossby waves at the solar tachocline. While the quadratic action of the sum of these three waves comprises the secondary beat period of 11.07 years, the main focus is now on the action of the even more pronounced period of 1.723 years. Our dynamo model provides oscillations with exactly that period, which is also typical for the quasi-biennial oscillation (QBO). Most remarkable is its agreement with Ground Level Enhancement (GLE) events which preferentially occur in the positive phase of an oscillation with a period of 1.724 years. While bimodality of the sunspot distribution is shown to be a general feature of synchronization, it becomes most strongly expressed under the influence of the QBO. This may explain the observation that the solar activity is relatively subdued when compared to that of other sun-like stars. We also discuss anomalies of the solar cycle, and subsequent phase jumps by 180 degrees. In this connection it is noted that the very 11.07-year beat period is rather sensitive to the time-averaging of the quadratic functional of the waves and prone to phase jumps of 90 degrees. On this basis, we propose an alternative explanation of the observed 5.5-year phase jumps in algae-related data from the North Atlantic and Lake Holzmaar that were hitherto attributed to optimal growth conditions.

astro-ph.SR↗

arXiv2023

Rieger, Schwabe, Suess-de Vries: The Sunny Beats of Resonance

We propose a self-consistent explanation of Rieger-type periodicities, the Schwabe cycle, and the Suess-de Vries cycle of the solar dynamo in terms of resonances of various wave phenomena with gravitational forces exerted by the orbiting planets. Starting on the high-frequency side, we show that the two-planet spring tides of Venus, Earth and Jupiter are able to excite magneto-Rossby waves which can be linked with typical Rieger-type periods. We argue then that the 11.07-year beat period of those magneto-Rossby waves synchronizes an underlying conventional $\alpha-\Omega$-dynamo, by periodically changing either the field storage capacity in the tachocline or some portion of the $\alpha$-effect therein. We also strengthen the argument that the Suess-de Vries cycle appears as an 193-year beat period between the 22.14-year Hale cycle and a spin-orbit coupling effect related with the 19.86-year rosette-like motion of the Sun around the barycenter.

astro-ph.SR↗

arXiv2023

No evidence for absence of solar dynamo synchronization

Context: The old question of whether the solar dynamo is synchronized by the tidal forces of the orbiting planets has recently received renewed interest, both from the viewpoint of historical data analysis and in terms of theoretical and numerical modelling. Aims: We aim to contribute to the solution of this longstanding puzzle by analyzing cosmogenic radionuclide data from the last millennium. Methods: We reconsider a recent time-series of $^{14}$C-inferred sunspot data and compare the resulting cycle minima and maxima with the corresponding conventional series down to 1610 A.D., enhanced by Schove's data before that time. Results: We find that, despite recent claims to the contrary, the $^{14}$C-inferred sunspot data are well compatible with a synchronized solar dynamo, exhibiting a relatively phase-stable period of 11.07 years, which points to a synchronizing role of the spring tides of the Venus-Earth-Jupiter system.

astro-ph.SR↗

arXiv2020

Phase coherence and phase jumps in the Schwabe cycle

Guided by the working hypothesis that the Schwabe cycle of solar activity is synchronized by the 11.07 years alignment cycle of the tidally dominant planets Venus, Earth and Jupiter, we reconsider the phase diagrams of sediment accumulation rates in Lake Holzmaar, and of methanesulfonate (MSA) data in the Greenland ice core GISP2, which are available for the period 10000-9000 cal. BP. Since some half-cycle phase jumps appearing in the output signals are, very likely, artifacts of applying a biologically substantiated transfer function, the underlying solar input signal with a dominant 11.04 years periodicity can be considered as mainly phase-coherent over the 1000 years period in the early Holocene. For more recent times, we show that the re-introduction of a hypothesized "lost cycle" at the beginning of the Dalton minimum would lead to a real phase jump. Similarly, by analyzing various series of $^{14}$C and $^{10}$Be data and comparing them with Schove's historical cycle maxima, we support the existence of another "lost cycle" around 1565, also connected with a real phase jump. Viewed synoptically, our results lend greater plausibility to the starting hypothesis of a tidally synchronized solar cycle, which at times can undergo phase jumps, although the competing explanation in terms of a non-linear solar dynamo with increased coherence cannot be completely ruled out.

astro-ph.SR↗

arXiv2019

Numerical and Experimental Investigation of Electro-Vortex Flow in a Cylindrical Container

In a cylindrical container filled with an eutectic GaInSn alloy, an electro-vortex flow (EVF) is generated by the interaction of a non-uniform current with its own magnetic field. In this paper, we investigate the EVF phenomenon numerically and experimentally. Ultrasound Doppler Velocimetry (UDV) is applied to measure the velocity field in a cylindrical vessel. Second, we enhance an old numerical solver by taking into account the effect of Joule heating, and employ it for the numerical simulation of the EVF experiment. Special focus is laid on the role of the magnetic field, which is the combination of the current induced magnetic field and the external geomagnetic field. For getting a higher computational efficiency, the so-called parent-child mesh technique is applied in OpenFOAM when computing the electric potential, the current density and the temperature in the coupled solid-liquid conductor system. The results of the experiment are in good agreement with those of the simulation. This study may help to identify the factors that are essential for the EVF phenomenon, and for quantifying its role in liquid metal batteries.

physics.flu-dyn↗

arXiv2019

Schwabe, Gleissberg, Suess-de Vries: Towards a consistent model of planetary synchronization of solar cycles

Aiming at a consistent planetary synchronization model of both short-term and long-term solar cycles, we start with an analysis of Schove's historical data of cycle maxima. Their deviations (residuals) from the average cycle duration of 11.07 years show a high degree of regularity, comprising a dominant 200-year period (Suess-de Vries cycle), and a few periods around 100 years (Gleissberg cycle). Encouraged by their robustness, we support previous forecasts of an upcoming grand minimum in the 21st century. To explain the long-term cycles, we enhance our tidally synchronized solar dynamo model by a modulation of the field storage capacity of the tachocline with the orbital angular momentum of the Sun, which is dominated by the 19.86-year periodicity of the Jupiter-Saturn synodes. This modulation of the 22.14 years Hale cycle leads to a 193-year beat period of dynamo activity which is indeed close to the Suess-de Vries cycle. For stronger dynamo modulation, the model produces additional peaks at typical Gleissberg frequencies, which seem to be explainable by the non-linearities of the basic beat process, leading to a bi-modality of the Schwabe cycle. However, a complementary role of beat periods between the Schwabe cycle and the Jupiter-Uranus/Neptune synodic cycles cannot be completely excluded.

astro-ph.SR↗

arXiv2016

The Tayler instability at low magnetic Prandtl numbers: Chiral symmetry breaking and synchronizable helicity oscillations

The current-driven, kink-type Tayler instability (TI) is a key ingredient of the Tayler-Spruit dynamo model for the generation of stellar magnetic fields, but is also discussed as a mechanism that might hamper the up-scaling of liquid metal batteries. Under some circumstances, the TI involves a helical flow pattern which goes along with some alpha effect. Here we focus on the chiral symmetry breaking and the related impact on the alpha effect that would be needed to close the dynamo loop in the Tayler-Spruit model. For low magnetic Prandtl numbers, we observe intrinsic oscillations of the alpha effect. These oscillations serve then as the basis for a synchronized Tayler-Spruit dynamo model, which could possibly link the periodic tidal forces of planets with the oscillation periods of stellar dynamos.

astro-ph.SR↗

arXiv2016

Synchronized helicity oscillations: a link between planetary tides and the solar cycle?

Recent years have seen an increased interest in the question of whether the gravitational action of planets could have an influence on the solar dynamo. Without discussing the observational validity of the claimed correlations, we ask for a possible physical mechanism that might link the weak planetary forces with solar dynamo action. We focus on the helicity oscillations that were recently found in simulations of the current-driven, kink-type Tayler instability, which is characterized by an m=1 azimuthal dependence. We show how these helicity oscillations can be resonantly excited by some m=2 perturbation that reflects a tidal oscillation. Specifically, we speculate that the 11.07 years tidal oscillation induced by the Venus--Earth--Jupiter system may lead to a 1:1 resonant excitation of the oscillation of the alpha-effect. Finally, in the framework of a reduced, zero-dimensional alpha--Omega dynamo model we recover a 22.14-year cycle of the solar dynamo.

astro-ph.SR↗

arXiv2014

The influence of current collectors on Tayler instability and electro-vortex flows in liquid metal batteries

The Tayler instability is a kink-type flow instability which occurs when the electrical current through a conducting fluid exceeds a certain critical value. Originally studied in the astrophysical context, the instability was recently shown to be also a limiting factor for the upward scalability of liquid metal batteries. In this paper, we continue our efforts to simulate this instability for liquid metals within the framework of an integro-differential equation approach. The original solver is enhanced by multi-domain support with Dirichlet-Neumann partitioning for the static boundaries. Particular focus is laid on the detailed influence of the axial electrical boundary conditions on the characteristic features of the Tayler instability, and, secondly, on the occurrence of electro-vortex flows and their relevance for liquid metal batteries.

physics.flu-dyn↗

arXiv2012

DRESDYN - A new facility for MHD experiments with liquid sodium

The DREsden Sodium facility for DYNamo and thermohydraulic studies (DRESDYN) is intended as a platform both for large scale experiments related to geo- and astrophysics as well as for experiments related to thermohydraulic and safety aspects of liquid metal batteries and liquid metal fast reactors. The most ambitious projects in the framework of DRESDYN are a homogeneous hydromagnetic dynamo driven solely by precession and a large Taylor-Couette type experiment for the combined investigation of the magnetorotational instability and the Tayler instability. In this paper we give a short summary about the ongoing preparations and delineate the next steps for the realization of DRESDYN.

physics.flu-dyn↗